Graphics Reference
In-Depth Information
The order of the noise curve can be either
cubic or quintic. The cubic curve is
C
1
(slope)
continuous everywhere, while the quintic curve
is
C
2
(curvature) continuous.
If value noise is used, the slope at each
noise point can be artificially set to zero (hori-
zontal) or can be smoothed using a Catmull-
Rom slope.
Notice that one of the control points for the
1D noise function is highlighted in green in the
1D noise function shown in Figure 10.17. When
a point is selected (by pointing to it and click-
ing the left mouse buton), its information can
be edited as follows:
Figure 10.17.
The four-octave value+gradient
1D noise function with quintic interpolation
described above.
•
The point can be moved up and down using the mouse, if the type of
noise is value-only or value+gradient.
•
The Gradient slider can be adjusted if the noise type is gradient-only
or value+gradient. If the noise uses quintic interpolation, the Curvature
slider can also be adjusted.
The other important option for noise is the Turbulence check box. When
this is checked, the individual octaves' absolute values are summed to deter-
mine the noise function's value.
Figure 10.18.
The 2D noise function defined above with rainbow (left), sky (center), and fire (right) color
scales.
